1. Technical Field
Example embodiments relate to a semiconductor memory device, and more particularly to a phase change memory device and/or a computing system including the phase change memory device.
2. Description of the Related Art
Semiconductor memory devices for storing data may be classified into volatile memory devices and non-volatile memory devices. The volatile memory devices are typically configured to store data by charging or discharging capacitors in memory cells, and widely used as main memories of various apparatuses. The volatile memory devices such as Dynamic Random Access Memory (DRAM) and Static Random Access Memory (SRAM) retain stored data while power is supplied and lose the stored data when power is off.
The non-volatile memory devices such as flash memory devices may maintain stored data even though power is off, and are widely used for storing program codes and/or data in computers, mobile devices, etc.
According to demands for high memory capacity, high operational speed and low power consumption of the memory devices, new memory devices of various types have been developed to realize high integration rate of DRAM, high speed of SRAM and non-volatility of flash memory in a single memory device. For example, Phase Change Random Access Memory (PRAM) using phase change materials, Resistance Random Access Memory (RRAM) using materials having variable resistance such as transition-metal oxides, and Magnetic Random Access Memory (MRAM) using ferromagnetism materials are attracting attention as memory devices of the next generation. Such materials have common characteristics that a resistance thereof is variable depending on magnitude and/or direction of applied voltage and/or current, and that the resistance can be maintained (that is, non-volatility) even though the applied voltage and/or current is intercepted and thus refresh operation is not required.
Each memory cell of the resistive memory devices may be formed with one resistive element and one switching element so that data may be stored by controlling voltage and/or current of a bit line and a word line to change resistance of the resistive element.
Because much time is required to program data in the resistive memory devices, particularly in the PRAM device, it is desirable to increase a programming speed of the resistive memory devices.